The present invention is directed to a device for driving nails or similar fastening elements and includes a driving member rotated by a motor, a driven member including means for converting rotational movement into translational movement for a driver rod, and a clutch for transmitting torque from the driving member to the driven member.
Driving devices powered by a variety of power sources are known for driving nails or similar fastening elements. For example, compressed air, combustion gases or electrical current may serve as the power source. While compressed air devices provide only a low output and require a supply of compressed air often not available at a construction site, in the case of devices powered by combustion gases there is a certain safety risk due to the danger of explosion of the gases. Electrically driven devices do not have any of these disadvantages. A known driving device, powered by an electric motor, has a driving member rotated by the motor and an output member which can be coupled with it for the transmission of the rotational movement. The output or driven member is connected with a driver rod by a part in the form a coiled flat spring. When the driven end is rotated in one direction, the spring band is unwound and the driver rod is displaced in the driving direction. The return movement of the driver rod is effected by a separate device.
The driving member is a satellite of a planetary gear with the satellite in meshed engagement with the inner gear system of a ring gear. A pin supported in the center of the satellite engages with the driven member.
When the device is idling, the ring gear is freely rotatable so that rotation of the satellite around its axis causes rotation of the ring gear. By pressing the device against a work surface, the ring gear is prevented from turning in the housing by a sensing element and a clamping spring whereby the satellite, rotating around its own axis, rolls on the internal gearing of the ring gear and, as a result, rotates around the axis of the driving pinion forming the sun gear. Accordingly, the satellite provides rotational movement to the driven member.
A disadvantage of this driving device is that the driving force as well as the length of the driving stroke is determined by the intensity and the time period during which the device is pressed against the work surface. These factors are influenced manually by the operating personnel. Further, the return movement of the driving rod into its initial position is not possible via the driven member and, as a result, the above-mentioned separate means are required.